Yes, the mFlexPIFA can be mounted directly to a metal surface.

Recommendations on placement and ground plane size is available in the datasheet:
mFlexPIFA
mFlexPIFA Dual Band

Ezurio, generally speaking, does not submit antennas for burn testing so as to be UL certified.  That said, we do use UL-94/V0 compliant materials for specific parts such as a radome.  These parts are identified on the antenna's datasheet.

In a cluttered propagating environment, such as a medical suite, office, etc. where there are many metal obstructions.
As a propagating signal encounters an obstruction, the antenna's polarization sense changes and will continue to change as each obstruction is encountered.
The FlexPIFA antenna mitigates this polarization sense issue by providing energy in both vertical and horizontal polarization; thereby, increasing the probability of picking up a useable signal.

    
dBd is a unit of measure for gain using a dipole as a reference; whereas, dBi uses an isotropic radiator.  To convert from dBd to dBi simply add 2.15 to the dBd value to get the dBi value (e.g. 0 dBd= 2.15 dBi)